1. Field of the Invention
This invention relates in general to cyclones and more particularly to especially configured cyclones with a liner system and method by which worn liners are replaced with a minimal expenditure of time and labor and without having to remove the cyclones from their mounting bases.
2. Description of the Prior Art
Cyclones are mechanisms that are used in various industries to separate different sized particles that are fed as a mixture into the inlet of the cyclone. In the mineral processing industries such as for example in the processing of copper, iron ore, lead/zinc, gold, coal and the like, a plurality of large cyclones are typically carried in mounting bases arranged in a cluster over a “tub”. Each of the cyclones are in circuit with grinding mills and a slurry of water and the mineral to be classified is fed into the inlet of the cyclone. The heavier materials in the slurry exit the cyclone through an underflow outlet at the bottom of the cyclone and are returned to the grinding mill. The lighter materials are carried upwardly in a vortex created within the cyclone and exit through an overflow outlet nozzle at its upper end. The primary components of a cyclone include an inlet housing having a feed duct and a cylindrical head section, a head section cover plate, a downwardly tapering conical housing depending from the head section, an apex cone at the lower end of the conical housing with the course material underflow outlet at the lower end of the apex cone, and an internal vortex finder coupled to the fine materials overflow outlet nozzle.
The feed duct of cyclones is often referred to as an involute which receives the slurry at high velocity from the grinding mill and directs it tangentially into the cylindrical head section of the cyclone. As the slurry swirls around in the head section the weight of the slurry, and particularly the large particles, will tend to fall downwardly into the conical housing of the cyclone. The larger particles and the water carrying them will move downwardly through the apex cone and will exit the cyclone through the underflow outlet. A vortex consisting of smaller particles and the water carrying them is created within the apex cone and moves upwardly through the center of the conical housing into the vortex finder and exits the cyclone through the overflow outlet.
The feed duct, inlet head section, head section cover plate, conical housing, apex cone and the vortex finder of large cyclones of the type used in mineral processing are provided with liners which protect these components from the destructive forces imparted by highly abrasive slurries as they move through the cyclones.
As disclosed in a paper entitled “Krebs Elastomer Liner Installation Instructions”, which is available on the internet at the krebs.com web site, gum rubber is the most commonly used liner material and synthetic rubber materials are also used in applications where gum rubber is not well suited. Such synthetic rubber-like materials include Neoprene, Nitrile/bunaN, Butyl, urethane and the like. Elastomeric liners are molded structures which historically are provided with annular flanges that are secured between the mating flanges of the different cyclone housing components to hold the liners in place. It is a common practice to affix these molded liners to the interior walls of the cyclone components by means of a suitable adhesive. The liners are designed to be a form fit within their respective components and compressive forces are used to install and fit the liners within each of the housing components and these forces must be maintained while the adhesive cures. In large cyclones, such as those having head section diameters of 26, 30, 33 inches, the conical housing is an assembly usually formed of two or more cone shaped housings which are bolted together at their mating flanges, and the conical housing assembly is similarly bolted to the lower end of the cylindrical head section after the large one piece liner is installed in the head section. The apex cone is bolted to the lower end of the conical housing assembly in some cyclones while others are attached by a quick release clamp as disclosed in my U.S. Pat. No. 4,541,934. In liner replacement operations involving these elastomeric liners, the cyclone housing must be disassembled, that is, the apex cone, the two or more cone shaped housings which form the conical housing assembly and the inlet housing are separated from each other and the head section cover plate is removed. This provides the access needed to peal the worn liners out of the several cyclone housing components and subsequently to apply the adhesive, install the new liners and exert the compressive forces needed to fit new liners.
As hereinbefore discussed, gum rubber is the most commonly used liner material and this is due to it providing the longest possible wear life in most applications. Alternative liner materials are used in applications where natural gum rubber is unsuitable. Synthetic rubber is used when temperature or the slurry constituents do not allow the use of natural gum rubber. Reinforced highly resilient urethane in used in applications in which rubber liners are torn rather than worn. Ceramic and silicone materials are typically used in high wear areas of the cyclone and, for example, in the coal industry such liner materials are used throughout the entire cyclone. As was the case with the replacement of rubber liners, the entire cyclone must be disassembled to accomplish replacement of the liners formed of these alternate materials. Typical installation of such liners is discussed in a paper entitled “Installation of Ceramic Parts into Krebs D-Series Cyclones” which is available on the internet at the krebs.com web site. These types of liners are molded or cast and are assembled and fit individually into the disassembled housing components which form the cyclone. The inlet head section liner is a large one piece structure which is inserted into the inlet head housing and rubber wedges are used to center the liner in the head section. The cover plate and cover plate liner is then mounted on the inlet housing which is turned upside down. The liners are inserted into the cone shaped sections and gaskets and spacer rings are then inserted sequentially between the flanges which join the inlet head section to the uppermost cone portion, and between the flanges which join the two or more conical sections to each other. The gaskets are sized so that the abutting edges of the liners are in contact with each other and a bead of silicone sealant is applied to the abutting edges to aid in sealing the joints. The liner is then inserted into the apex cone and it is then connected to the lowermost cone section of the conical housing. The cyclone is then set on its side and the feed duct and vortex finder are then attached to complete the reassembly of the cyclone.
Disassembly of large cyclones for the purpose of replacing worn liners is very labor intensive and time consuming. The first problem associated with such operations is the need for removal of the cyclone from its mounting base in the cluster of cyclones and transporting it to a dedicated repair facility or simply laying it on its side in a suitable maintenance area away from the cluster. Cyclones of this type are very awkward and can weigh up to about 5,000 pounds. Thus, the operator of the crane needed to remove and transport the cyclone must be careful not to damage the cyclone or adjacent equipment and must be skillful to precisely align the cyclone for reconnection to the material handling pipes when it is being returned to its operational position. The second problem in such operations is removal of the multiplicity of nuts and bolts which hold the various cyclone components together and typically the nuts and bolts will number between 50 and 75 depending on the size of the cyclone. There are some places on cyclones where power tools will not fit and in all cases the cyclones which are laying on their sides during this phase of the replacement operation must be moved to provide the needed access. Further, due to the hostile environment in which cyclones operate, the nuts and bolts are often rusted and must in many instances be heated or cut off to remove them.
The traditional way to determine when cyclones are in need of liner replacement is to periodically inspect the liners until accurate records of the wear characteristics are collected at which time replacement schedules can be established based upon operating time. Conducting periodic inspections of the liners is labor intensive in that access to the interior of the cyclones is needed to conduct the inspections and of course operation of the cyclone must be interrupted during the inspections.
Therefore, a need exist for a new and useful cyclone with a special liner replacement system and method which overcomes some of the problems and shortcomings of the prior art.